Useful candidates for thin film semiconductor and conductor layers for thin-film transistor (TFT) applications include indium zinc oxide (IZO), gallium zinc oxide (GZO), aluminum zinc oxide (AZO), and boron zinc oxide (BZO).
These materials can be used in TFTs, flat-panel displays, optoelectronics and other devices and products. The materials IZO, GZO and AZO can be used for electrodes in displays, touch screen displays, solar cells and other applications.
Significant drawbacks in the production of devices using these materials are slow manufacturing process speed and throughput, as well as non-uniformity of the composition of deposited layers. These drawbacks are mainly due to vacuum deposition methods used in the conventional production of various devices.
For example, large scale manufacturing of TFTs, transparent thin-film transistors (TTFTs) and related thin film devices using conventional vacuum-based processes can be unpredictable because of the difficulty in controlling numerous chemical and physical parameters involved in forming a semiconductor or conductor layer of suitable quality on a substrate, both reproducibly and in high yield.
Attempts to increase the efficiency and speed of manufacturing TFT/TTFT materials include use of liquid deposition/printing methods in which particles or precursors for the materials are deposited from an ink. However, ink compositions using components made by sol-gel processes, or that contain nanoparticles, can have drawbacks because they lack stability and compositional uniformity. Their instability is due to the formation of aggregates, particulates or precipitates that cause clogging, blocking or constriction of printing equipment.
Another drawback in the production of thin film transistors is the inability to control the stoichiometry of the product materials. With existing methods and approaches, many useful material compositions are difficult to make because of the lack of control of the stoichiometry. A significant problem is the need to create thin films of semiconducting and conducting materials with controlled compositional homogeneity, uniformity and purity.
There is a long-standing need for solution-based processes for making semiconducting and conducting materials having a predetermined stoichiometry for thin film applications.
There is a need for stable ink compositions made from molecular precursor compounds that are completely soluble so that the ink can be used in a high speed and high yield printing process for making semiconducting and conducting materials for thin film transistors.
What is needed are compounds and compositions to produce semiconductor and conductor materials from solution-based processes for thin film transistors, display devices and other products.